diff --git a/lib/asset-manifest-generator.js b/lib/asset-manifest-generator.js
index f528c3e..2c3f6c8 100644
--- a/lib/asset-manifest-generator.js
+++ b/lib/asset-manifest-generator.js
@@ -7,6 +7,19 @@ var fs = require('fs-extra');
 
 var DEFAULT_SUPPORTED_TYPES = [ 'js', 'css' ];
 
+/**
+ * Adds a bundle if it doesn't already exist
+ *
+ * @name addBundleToManifest
+ * @param {Object} manifest The existing manifest object
+ * @param {string} bundleName The bundle to add
+ */
+function addBundleToManifest(manifest, bundleName) {
+  manifest.bundles[bundleName] = manifest.bundles[bundleName] || {
+    assets: []
+  };
+}
+
 /**
  * A Broccoli plugin to generate an asset manifest from a given input tree.
  * You can also provide a second tree that is a tree containing an existing
@@ -83,19 +96,10 @@ AssetManifestGenerator.prototype.build = function() {
       return manifest;
     }
 
-    if (bundleInfo.isNewBundle) {
-      if (manifest.bundles[bundleName]) {
-        throw new Error('Attempting to add bundle "' + bundleName + '" to manifest but a bundle with that name already exists.');
-      }
-
-      manifest.bundles[bundleName] = {
-        assets: []
-      };
-    }
-
     // If the asset is named "dependencies.manifest.json" then we should read
     // the json in and set it as "dependencies" on the corresponding bundle.
     else if (assetName === 'dependencies.manifest.json') {
+      addBundleToManifest(manifest, bundleName);
       var dependencies = fs.readJsonSync(path.join(inputPath, entry));
       manifest.bundles[bundleName].dependencies = dependencies;
     }
@@ -109,6 +113,7 @@ AssetManifestGenerator.prototype.build = function() {
       let contents = fs.readFileSync(fullPath, 'utf-8');
 
       if (contents.trim() !== '') {
+        addBundleToManifest(manifest, bundleName);
         manifest.bundles[bundleName].assets.push({
           uri: generateURI(path.posix.join(prepend, entry)),
           type: assetType
diff --git a/node-tests/fixtures/manifests/txt.json b/node-tests/fixtures/manifests/txt.json
index f0f8873..9b6fe4e 100644
--- a/node-tests/fixtures/manifests/txt.json
+++ b/node-tests/fixtures/manifests/txt.json
@@ -13,9 +13,6 @@
       "assets": [
         { "uri": "/bundles/chat/assets/secret.txt", "type": "txt" }
       ]
-    },
-    "shared": {
-      "assets": []
     }
   }
 }
diff --git a/node-tests/manifest-generator-test.js b/node-tests/manifest-generator-test.js
index 27d8fb9..39abfd0 100644
--- a/node-tests/manifest-generator-test.js
+++ b/node-tests/manifest-generator-test.js
@@ -151,7 +151,7 @@ describe('manifest-generator', function() {
       yield output.build();
       var manifest = fs.readJsonSync(output.path('asset-manifest.json'));
 
-      assert.deepEqual(manifest.bundles.chat.assets, []);
+      assert.strictEqual(manifest.bundles.chat, undefined);
     }));
   });
 })